Galaxy — a spiral arm of stars

Galaxy is a galaxy simulator that paints a slowly rotating spiral galaxy. Hundreds of stars orbit the center at differential speeds (inner stars spin faster than outer — Keplerian-ish). Click anywhere to add a star: it joins the rotation and traces an arm over time. The arms themselves are a density wave, like in real spiral galaxies: the spiral pattern turns as one piece, young stars are born inside an arm, drift along their own orbit, fade and are reborn in an arm, so the spiral stays sharp however long you watch.

How to play

Click to add a star at that position. Drag to give the whole galaxy a spin push — pull it clockwise or counter. The center has a subtle bulge that brightens with star count.

Why it's satisfying

Spiral galaxies are one of the most universally recognized cosmic shapes. Watching one rotate at a meditative pace, knowing you can sprinkle in your own stars, gives a small godlike calm.

About

Galaxy is part of Alcy, free contemplative micro-games. For more cosmos: Constellation, Orbit, Tunnel.